If you depend on dynamic remote content, I'm afraid there's not a simple solution. The thing is, if yoy try to preload those images on your own, it would raise the same performance hit.

Only if those images are static, i.e. they really don't change on a daily basis, you can run nightly cron task to fetch all remote resources and then to serve them on your (hopefully) supercharged nginx web server alongside Phalcon.